If you're following -RELEASE, you need to wait for 4.9 to be released, if you're following -STABLE, you need to checkout the system source and rebuild, and if you're running -CURRENT (my favorite), you need to download a snapshot bsd.rd, boot from it, perform the upgrade, reboot, run sysmerge -s /path/to/etcXX.tgz (usually the same mirror you got the bsd.rd from, though that's not 100% critical), then pkg_add -u. Alternatively, you can download the source and build it for -CURRENT.

I assume you are asking how to update all installed packages. See the pkg_add(1) manpage, & specifically look at the -u switch. This is also covered in Section 15.2.6 of the FAQ.

As mentioned before, studying the FAQ will save you significant time & aggravation.

Otherwise, if you are asking about updating the system itself, study the Upgrade Guide. When OpenBSD 4.9 is publicly released, this document will be updated with information pertaining to OpenBSD 4.8 --> OpenBSD 4.9.

OpenBSD's documentation is very good & concise. Studying what is posted on the official Website is highly recommended.

Yes, I study the documents
But I want to specialize the system and completed the study
Did not mean a package upgrade or a program but a full system upgrade, not 4.9
Upgrade kernel + GNOME + exploit system
Until the system remains protected from hackers
thank you